Uplink Grant Reactivation for Low-Latency Cell Handover
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Solution Overview
Problem
Existing wireless communication systems face challenges in reducing latency and signaling overhead during cell handover processes, particularly in L1/L2 triggered mobility scenarios, due to the need for RRC signaling and Layer 3 reconfiguration, which results in long delays and interruptions.
Innovation Solution
A method and apparatus that enable the activation of uplink grants without RRC reconfiguration by using MAC or physical layer signaling to clear and reactivate uplink grants during cell handover, specifically for configured grant types 1 and 2, thereby reducing latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RRC signaling-triggered reconfiguration with synchronization is used for cell handover, then the handover process is reliable and standardized, but the latency and signaling overhead increase significantly
Solution Approach 1:
The uplink grant is pre-configured by RRC signaling before handover occurs. When the timeAlignmentTimer expires and the cell is reconfigured, the pre-configured uplink grant can be quickly activated without needing new RRC signaling, thus reducing handover latency while maintaining reliability through the preliminary configuration setup
Solution Approach 2:
The patent extracts the uplink grant configuration from the RRC reconfiguration process and handles it separately through MAC layer signaling. This separation allows the uplink resources to be activated independently and more quickly during handover, reducing the overall signaling overhead and latency while maintaining the reliability of the handover process
2Reliability
If RRC signaling is used to activate uplink grant during handover, then the uplink resources are properly allocated, but the signaling overhead and interruption time increase
Solution Approach 1:
The patent introduces MAC layer signaling as an intermediary between RRC configuration and actual uplink grant activation. The RRC layer configures the uplink grant in advance, and the MAC layer activates it during handover using less overhead signaling, thus maintaining proper resource allocation while reducing signaling complexity and overhead
Solution Approach 2:
The uplink grant is configured in advance by RRC signaling before handover occurs. When the timeAlignmentTimer expires and the cell is reconfigured, the pre-configured uplink grant can be quickly activated without needing new RRC signaling, thus reducing handover latency while maintaining reliability through the preliminary configuration setup
3Loss of time
If L1/L2 triggered mobility is implemented, then the latency and interruption time are reduced, but the uplink grant activation becomes more complex
Solution Approach 1:
The system uses self-service mechanisms where the MAC layer autonomously activates the pre-configured uplink grant based on the expiration of the timeAlignmentTimer and receipt of the cell reconfiguration message. This self-service approach at the MAC layer reduces the need for complex cross-layer coordination and simplifies the activation process during L1/L2 triggered mobility
Solution Approach 2:
The patent introduces MAC layer signaling as an intermediary between RRC configuration and actual uplink grant activation. The RRC layer configures the uplink grant in advance, and the MAC layer activates it during handover using less overhead signaling, thus maintaining proper resource allocation while reducing signaling complexity and overhead
Data Source
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AI summary
The present application discloses a method and apparatus in a node for wireless communication. The method comprises: a first node receiving first signaling, the first signaling being RRC signaling, and the first signaling being used for configuring uplink grant for a first cell; in response to an expiration of a first timer, clearing the uplink grant at least for the first cell; receiving second signaling, the second signaling being MAC layer signaling or physical layer signaling; and in response to receiving the second signaling, handing over to the first cell, wherein the behavior of handing over to the first cell comprises activating the uplink grant configured by the first signaling. According to the present application, the uplink resources can be quickly obtained in a cell handover scenario triggered by protocol layers lower than the RRC layer, the interruption time is shortened, and the signaling overhead is reduced.